t5531: further "matching" fixups

Commit 43eb9202 switched one of the sub-repository in this
test to matching to prepare for a world where the default
becomes "simple". However, the main repository needs a
similar change.

We did not notice any test failure when merged with b2ed944a
(push: switch default from "matching" to "simple", 2013-01-04)
because t5531.6 is trying to provoke a failure of "git push"
due to a submodule check. When combined with b2ed944a the
push still fails, but for the wrong reason (because our
upstream setup does not exist, not because of the submodule).
Signed-off-by: NJeff King <peff@peff.net>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

t/t5531-deep-submodule-push.sh

@@ -12,6 +12,7 @@ test_expect_success setup '
 	(
 		cd work &&
 		git init &&
+		git config push.default matching &&
 		mkdir -p gar/bage &&
 		(
 			cd gar/bage &&